Check digit calculator

Check Digit: The last digit of a bar code number is a computer Check Digit which makes sure the bar code is correctly composed.

GS1 Company Prefix (GCP): GCP is a part of the GS1 Identification number consisting of a GS1 Prefix and a Company Number, both of which are allocated by GS1 Organisations. GS1 India assigns GCP to its subscribers who administer the allocation of GS1 Identification numbers.

Check digit is calculated by using the digits present in GCP and Item ID parts of a GS1 identification number. This calculation, called the Modulo 10 algorithm, is same for all GS1 primary identification numbers.

Every time a computer decodes a GS1 barcode number it repeats the calculation and checks its answer against the check digit to verify the data integrity of the number.